1. Field of the Invention
The present invention relates to digital signal distributors for time division multiplex signals having the same frame format and for single-channel signals.
Basic systems encompassing 24 or 30 channels are known in the art for time division multiplex signals for transmitting voice or data. A number of such channels of a pulse frame are combined for audio programs. Higher hierarchy levels can be formed from these time division multiplex signals by means of Cigitial signal multiplexers. Video and picture telephony signals are also transmitted at these levels. Such a system is described, for example, in "Telcom-Report", 2 (1979) Special Issue, Digital Transmission at pages 16-20. Parallel signaling transmission required for voice signal transmission is described in the same periodical at pages 65-71.
In such known systems, given time multiplex combination of signals, full occupation of the defined pulse frame is not always guaranteed. This problem leads to uneconomical network structuring.
A channel distributor of the type described above is disclosed in German patent No. 2,538,392, corresponding to U.S. Pat. No. 3,997,728. This system does not include any frame adaptation means. As a consequence, transmission without information omission or repetition is possible only given a maximum jitter or drift of one bit, and only given synchronous time division multiplex signals. Information omission or repetition occurs in a frame at a random location. As a result thereof, the integrity of the frame, that is, the source of all byte values of the frame from the same scan cycle, is impaired.
As used herein, the term "jitter" means phase fluctuations having frequencies above approximately 0.01 Hz, and the term "drift" as used herein means frequencies below this frequency. Frame integrity exists when all byte values of a frame are derived from the same time unit.